Process of manufacturing reinforced-concrete pressure-pipes.



G. RAE.

PROCESS OF MANUFACTURING REINFORCED CONCRETE PRESSURE PIPES.

APPLICATION FILED JAN. 6, 1910.

1,1 07,235, Patented Aug. 11,1914.

GEORGE RAE, OF PORTLAND, OREGON.

.PROCESS OF MANUFACTURING REINFORCED-CONCRETE PRESSURE-PIPES.

Specification of Letters r a tent.

Patented Aug. 11, 1914.

Application filed'l'anuary e, 1910. s w no. 586,778.

To all whom it may concern Be it known that I, GEORGE RAE, a citizen ofthe United States, residing at 251 Tenth street, in the city ofPortland, county of Multnomah, and State of Oregon, have invented newand useful improvements in the process of manufacturingreinforced-concrete pressure-pipes designed or intended to resisttension stresses and analogous composite structures of materials havingproperties similar to those composing reinforced concrete, of which thefollowing is a specification.

This invention relates to improvements in the art or process ofmanufacturing pressure pipes or similar structures of combinations ofmaterials of diifering properties, by which the materials are united insuch a way as to efliciently utilize the more valuable properties of thevarious materials combined,

It is the experience of those familiar with the present state of the artof manufacturing reinforced concrete pressure pipes, that underpressures producing economical working stresses in the steel, finecracks are formed in the concrete by reason of the fact that concrete incombination with steel ruptures long before the steel has attained itssafe working stress.

The object of this invention is to obviate such injurious cracking inreinforcedconcrete pipe and like composite structures subject to tensilestresses by maintaining the continuity or integrity of the concrete.This process is particularly valuable in the manufacture of reinforcedconcrete pressure pipe and pipe of similar construction, also hoopedcolumn shells and the like.

I am aware that tension material iii a state of initial tension has beenembedded in green concrete heretofore, and also that rods, etc.,

have been put in tension during the hardening and contraction of theconcrete through the use of tensioning devices incorporated in thestructure. This invention is an improvement in that no tensioningdevices are incorporated and in that the concrete is normally in a stateof induced compression, which is automatically relieved concurrentlywith an increase in the initial 7 tensile stress in the steel to adesired amount upon the application of an internal working pressure.

TlllS invention relates to a new, novel, and

useful process for the manufacture of such combination structureswhereby the tension resisting material attains the desired workingstress without permitting such cracks to form, and in the case ofressure i e and hoopedcolumn shells, or the like, tens1on res1st1ngproperties of the steel or other tension resisting material areinitially available, without the preliminary deformation now necessaryto develop the full resistance of the structure.

Figure 1 shows across section of the core, together wlth a method ofapplying the process and a diagram of a device which may be used. Fig. 2shows a portion of pipe with the reinforcmg applied, the outer coatmg tobe apphed later being indicated by dotted lines forthe sake ofclearness.

In the drawing, A is the shell or core of suitable length, previouslyformed and hardeneg, embeddetc}1 inlwhich,dpreferably at the sur ace,are e on 'tu inal reinfo'r' rods B. clilg Q'and D are devices forholding end of hehcal reinforcement F.

E are guide rollers having a friction drag not shown.

Gr is the heating chamber containing an alloy or material of suitablemelting point, with stufling box I atweach end, and thermometer H toindicate the temperature within. I

J are burners fed from supply pipe L,

through the regulating valves K. The guide rollers and heating apparatusare mounted on a suitably moving carriage not shown, the movement ofwhich in conjunction with the rotary movement of the core A indicated bythe arrow 0, serves to apply the reinforcement F in the form of a helix.

The practical application of the process by the device shown is asfollows :The core A is centered in a lathe or similar machine capable-ofrota-ting it. The heating and guiding devices being mounted on a movablecarriage, are caused to move at a rate which in conjunction with therotary motion of A will. produce a helix of the desired pitch. Thesupply pipe L is connected by means of a flexible tube to a gas main orthe like. The reel of reinforcing material may also be mounted on themovable carriage. The

material F, having attained the desired temchamber Gr, passes over thegrooved guide rollers E whichthrough the action of the friction dragmentioned cause the material F to come into close cont-act with therotating core A. When the heated material F cools to the commontemperature, the core A is compressed to an extent dependent on thetemperature at which the material F is applied. It will be evident thatthe heating chamber G can be dispensed with by roducing an elongationequal to that attained by the heating, through or by means of a tensilestress produced by a suitable arrangement of friction drags. Whether thematerial F is applied heated or in an elongated condition produced bytensile stress, it will be evident that it will strongly grip the coreA, thereby securing the several turns of the helix in their designedposition without the use of devices for tying them to the longitudinalrods.

The data for the proper application of the process is determined bycalculation based on the physical properties of the materials involved.If concrete is to be used as the compression resisting material, itscompressive strength and modulus of elasticity are to be determined. Ifthe tension resisting material is to be steel, its tensile strength andmodulus of elasticity are necessary in calculating the proper relationand initial stresses of the materials. This invention makes it possibleto use steel of high tensile strength at its safe working stress.

As an example, the calculation for a 12- inch reinforced concretepipefor a pressure of 200 lbs. per square inch may be indicated,

assuming the following constants for the materials I Concrete, modulusof elasticity 3,000,000 lbs Concrete, ultimate compressive strength2,000 lbs. Steel, modulus of elasticity 80,000,000 lbs.

Steel, working stress, one-half elastic limit, say.- 20,000,000 lbs.

It is aimed to so adjust the relation between the steel and concretethat when the pipe is under its working pressure the steel will bestressed to 20,000 lbs. per square inch and the concrete will besubstantially under no tensile stress. As an example of the applicationof the process, the steps necessary for manufacturing a 12-inchreinforced concrete pipe designed for aninternal pressure of 200 lbs.per square inch will be indicated. A plain concrete pipe of 12- inchesinside diameter is made with a thickness of shell of l-inch. When thishas attamed a suitable compressive strength, say 2000 lbs. per squareinch, it is wound with steel having an area of square inch per inch oflength of pipe under a tension of 12,500 lbs. per square inch or at atemperature which will produce an elongation equal to that produced bythis tension. A simple calculation in accordance with well knownprinc'ples of mechanics Will show that the con ipression in the concretewill then be 750 lbs. per square inch, and when the completed structureis subjected to an internal pressure of 200 lbs. per square inch,

the compression in'the concrete will be reduced to zero, and the tensionin the steel Will be 20,000 lbs. per square inch. As a result of thiscondition the concrete will not be ruptured, and its tensile strengthwill act as a factor of safety in conjunction with the increased tensilestress in the steel if subjected to greater pressure than that providedfor in the construction. It is evident that the tension resistingmaterial can. be effectively applied to molded or cast cores of othermaterial possessing compressive strengths great in comparison with theirtensile strengths, as burnt clay, terra cotta, glass, etc., the initialtensile stress of the tension resisting material being adjusted inaccordance with the relations of the physical properties of thematerials used so that at the designed working stress there will besubstantally no tensile stress in the compression resisting material.

After the steel is applied as indicated, a protective coating of asuitable corrosion resisting or fire-proofing material is appliedexternally, and an interior coating of waterproofing material intendedto close the pores of the concrete may be applied. lhe steel or othertension resisting material may be effectively applied in a state oftension by a suitable means for producing the desired tension directlyor by indirect means as by its application at such a temperature thatwhen the steel or tension resisting material cools to the .temperatureof the concrete or other core, the desired tension will exist in thetension material and the desired compression in the compressionresisting material.

I claim:

1. An improved process of manufacturing reinforced concrete pressurepipe and similar composite structures consisting in the application ofthe steel or tension resisting material to a hardened shell or core ofconcrete or similar material in the form of a continuous helix in astate of tension of such degree as will induce a determinate beneficialrelation of stresses in the component parts of the structure, for thepurposes set forth.

2. An improved process for manufacturing reinforced concrete pressurepipe and similar structures consisting in the application of tensionmaterial as a helix inclosing a core or shell of hardened concrete, saidhelix of tension material being applied at such a temperature that 011cooling the induced compressive stress in the core will be of suchdegree that when the designed in ternal pressure is applied, there willbe a designed increased tensile stress in said helix, coincident with adesigned decreased compressive stress in said core or shell of concrete.

3. As an article of manufacture, a reinforced concrete pressure pipecomposed of a core or shell of concrete or similar matetension materialis thereby increased to a rial normally in a state of inducedperiphdesigned amount coincidently with a de- 1o eral compression,produced by an incasing signed decreased compressive stress in the helixof tension material normally in a state concrete core or shell.

of initial tension, the relations of cross sec- GEORGE RAE. tional areasand initial stresses being such Witnesses:

that when the pipe is subjected to the de- H. E. HEATH,

signed internal pressure, the tension in the WM. G. SAUNDERS.'

